中一英文數學問題，求解答！！！

As he answers 4 questions correctly, he will get 4X5 = 20 marks

But he scores -10, so his total mark for in correct questions is 20-(-10)= 30 marks

Also. questions not answered don't affect the score.

Questions he answers incorrecctly
= 20-(-10)/ -3
= 30/3
= 10

He answers10 questions incorrectly.

Let's check the answer.

4X5+(-3)X10
= 20-30
= -10

If David scores -10 marks and he only answers 4 questions correctly,how many
questions does he answer incorrectly?
如果David 得到了10分,佢只答對了4題,那他答錯多少題?

你係唔係差少少資料==
係唔係錯會扣分,唔答會扣或者唔扣之類...
因為這樣很難無啦啦會彈答案出來
或者可能我數學未夠班
如果假設有8題,總分20分
答對4題,那就錯了4題啦==

How many mark will be deducted in wrong ans.
How many question are there in total?